Computation of the centralizer dimension of generalized Baumslag–Solitar groups

A finitely generated group $G$ acting on a tree so that all vertex and edge stabilizers are infinite cyclic groups is called a generalized Baumslag-Solitar group ($GBS$ group). The centralizer dimension of a group $G$ is the maximal length of a descending chain of centralizers. In this paper we complete a description of centralizers for unimodular $GBS$ groups. This allows us to find the centralizer dimension of all $GBS$ groups and to establish a way to compute it.